Description: The investigators propose to examine the interactive accumulation, toxicity, and excretion of Hg, Cd, As, and Cr in rabbit kidney slices and in primary cultures of proximal renal tubular cells grown on porous membrane supports. The aim is to determine the effect of exposure to one metal on the kinetics and toxicity of the other metals, using in vitro systems and based on micro-PIXE analyses and biochemical indices of toxicity (e.g., K+/DNA ratio). The effects of certain metal ligands (GSH, MT, albumin) and chelators (DMPS) on the interactions will be tested.